The present invention relates to the finishing of wallboard panel joints in the course of interior construction, and more specifically to the filling of joints between adjacent panels using a combination of wallboard joint compound and tape.
In the construction field, and particularly in interior construction, walls are commonly formed with a plurality of abutting wallboard panels or the like used to construct interior walls. A wall joint is formed at a location where two panels meet. Such joints are either flat, when forming interior wall panels, or also at inside and outside corners when common edges of adjacent panels meet at angles to each other than 0 or 180°. To provide a smooth, continuous wall appearance, joint tape is applied to the wall joint. Tape is either applied to the wall joints by hand, or using devices commonly referred to as taper or taping tools.
Prior to the application of joint tape, it is customary to prefill the joint with joint compound. There are several categories of joint compounds. Drying type compounds harden through the evaporation of water, whereas setting type joint compounds chemically react with water during the curing process. Setting type joint compounds typically use calcium sulfate hemihydrate, also known as stucco or plaster of Paris, as a base. When water is added to the setting type powder, it reacts with the calcium sulfate hemihydrate via a hydration reaction to form an interlocking matrix of calcium sulfate dihydrate crystals. The interlocking crystal matrix gives the compound increased strength. The benefit of a setting type joint compound over a drying type is the overall strength of the finished joint, resulting in less shrinking and cracking, as well as an independence from having to wait for the joint compound to be completely dry prior to further finishing. Drying type joint compounds have the advantage of ease of use, as they typically come in a ready mixed form, with water being added and mixed by the manufacturer. A third type of joint compound combines the setting action of a calcium sulfate hemihydrate based compound with the ease of use of a ready mixed compound.
Taper or taping tools apply a viscous filling and adhering material in the form of joint compound to the joint tape and subsequently apply the compound and tape to a wall joint. Such joint compound is also commonly referred to as mud. A variety of taper tools, also referred to as automatic dispensing devices, exist in the market place, but the taper tools generally operate in a similar manner. Initially, the taper tool is used to apply the tape and joint compound to a wall joint. The tape exits the tool from its first or forward end. After the taper tool reaches the top or bottom of the joint (depending on which direction the operator is applying the tape and compound) and completes tape application for the particular wall joint, the operator activates a cutting mechanism used to cut the tape. Typically, the cutting mechanism is disposed on and behind the forward end of the taper tool.
Accordingly, for the next application of tape to the wall surface, the tape must be advanced to the forward end of the taper tool. This can be performed by either manually grasping the tape and feeding the tape to the forward end, or by a tape advancing assembly, which is also connected to the taper tool. The tape advancing assembly is actuatable by the operator and engages the tape to advance the leading edge of the tape toward the forward end of the taper tool. Suitable exemplary taping tools are disclosed in U.S. Pat. Nos. 4,086,121; 5,882,691; 6,581,805; 6,874,557; 7,624,782 and US Patent Application Publication No. US 2007/0261334, all of which are incorporated by reference.
Unfortunately, in many cases, advancing the leading edge of the tape in either of these manners does not provide tape with sufficient wallboard joint compound applied. Accordingly, the portion of the tape without compound will not stick to the wall surface and will not provide an effective seal between wall sections. Thus, many applicators apply the extra required wallboard joint compound by hand. Other drawbacks of conventional taping tools relate to the significant volume of joint compound required for properly adhering the tape to the wall joint, and the frequent difficulty in obtaining a good adhesive bond between the tape and the joint.
Mechanical pre-fill tool applicators, also known as finishing boxes are known in the art and are described in U.S. Pat. Nos. 2,824,442; 2,889,699; and 2,984,857 incorporated by reference, among others. Such devices include an enclosed, wedge-shaped hopper having a generally flat surface facing the wallboard joint, and provided with an elongate opening or gate through which the joint compound is extruded. Opposite the flat surface, the hopper is defined by a movable pressure plate. Once the hopper is filled with joint compound, the user places the device on the joint, and exerts pressure on the pressure plate as the unit is drawn down the length of the joint. This operator-generated pressure is often exerted through the use of an elongated extension handle that is well known in the art. As the pressure plate moves towards the gate, the wallboard joint compound is extruded into the joint. A screed or wiper bar or blade is often provided to smooth the extruded joint compound.
Such devices are usually used for flat joints having both tapered and square edges. Variations of these devices are used to finish inside corner or angle joints. The latter group of devices is disclosed in U.S. Pat. Nos. 5,263,836; 4,451,223 and 3,932,101. These mechanical applicator devices effectively and efficiently dispense the necessary amount of material to adequately pre-fill a joint prior to taping and finishing. The novel mechanical applications are superior in terms of speed and reproducibility compared to the widespread job practice of manual hand application methods with a broad knife or trowel.
However, known finishing boxes have encountered inconsistent results in providing smooth, suitably tapered and/or flat wallboard joints. Also, the conventional corner tools are relatively complicated to operate by many applicators.
Accordingly, there is a need for an improved system for applying sufficient amounts or wallboard joint compound to wallboard joints that addresses the shortcomings of the conventional practices discussed above.